Taxotere (N-debenzoyl-N-tert-butoxycarbonyl-10-deacetyl Taxol; RP 56976; NSC 628503) is a semisynthetic analogue of Taxol. It is twice as active in inhibiting tubuline depolymerization and has a better in vivo activity on B16 melanoma, with responses in advanced colon 38 and PO3 adenocarcinoma. Sixty-five patients (49 women, 16 men), with a median age of 57 years, received 248 courses of Taxotere given as a 1–2-h i.v. infusion every 2 or 3 weeks. Ten distinct dose levels from 5 to 115 mg/m2 were studied. Dose-dependent, reversible neutropenia was the limiting toxicity. Delayed and cumulative skin reactions occurred beyond 70 mg/m2. Alopecia was observed in the majority of patients beyond 70 mg/m2. Four partial responses were achieved in patients with ovarian carcinoma, breast carcinoma, small cell lung cancer, and carcinoma with unknown primary. The pharmacokinetics of Taxotere, determined in 23 patients receiving 20 to 115 mg/m2, was linear. At the highest doses, the Taxotere plasma profile was typically triphasic, with a terminal half-life of 13.5 ± 7.5 (SD) h, a plasma clearance of 21.1 ± 5.3 liters/h/m2, and a distribution volume of 72 ± 40 liters/m2. AUC correlated with the percentage decrease of neutrophils in a sigmoid Emax model. The renal excretion of unchanged Taxotere was very low (<5% of the dose). The recommended dose for phase II trials with this schedule is 100 mg/m2 every 3 weeks.